I’m having a hard time emotionally/hormonally and I’m in the middle of shiva nekiiym. In an angry fit to myself, I thought to myself: “today is day nothing”. (BH I have very good shalom bayis but I was just in a very bad state. ) As I got to the end of the thought so to speak, I thought “of course not”/nevermind. Because I had that thought, is that a hefsek in my counting?
It is not a hefsek in your counting and you can continue regular. The reason is that even according to those who say that a woman has to count her clean days, it is only if she stopped counting for a while, (at least half a day). Additionally, you didn’t actually stop counting for any reason, your mind was just playing games with you.
Minchas Yitzchok 4-73, Shiurei Shevet Halevi 196-4 (4), Pischei Halacha NIda Vol. 2 pg. 200, Levushei Oz 196 tamtzit 7, Ashrei Hoish Y:D chap. 32-11.